1) Field of the Invention
The present invention relates to a graphite intercalation compound having a lower resistivity for use as a conductive material, more specifically to a graphite intercalation compound containing a metal halide as the guest and also relates to a method for producing the same.
2) Description of the Related Art
Graphite intercalation compounds are compounds wherein atoms, molecules and ions are intercalated into graphite. The practical value thereof has been drawing attention recently because of the improved functional properties such as the low resistivity comparable to metal and the excellent discharge and frictional properties and also because of the relatively easy synthesis.
Because the graphite intercalation compounds, incorporating as the intercalates metal halides such as FeCl.sub.3, CuCl.sub.2 and the like, demonstrate a higher conductivity and are substantially stable in the atmosphere, the application thereof as conductive materials is now expected.
It is known that the graphite intercalation compounds containing a metal halide as the intercalate can be synthesized and produced by reacting graphite with a metal halide at a predetermined temperature according to a mixing method.
The present inventors have carried out the environmental test of known graphite intercalation compounds (abbreviated as GIC often hereinafter) containing metal halides as the intercalate in an atmosphere of a high humidity. They have found that in such an atmosphere the change with time of the resistance value of NiCl.sub.2 --CuCl.sub.2 --GIC, otherwise considered to be stable, is large.
In order to apply a conductive paste containing a metal halide GIC dispersed in an organic binder to an electronic device, it must be guaranteed that the properties thereof won't change in actual environment for a long period of time. It is certainly known that the GIC is stable to heat up to about 200.degree. C. However, when an environmental test was carried out in such a manner that the paste was printed and thermally cured to experimentally make an electric conductor which was then left to stand in an atmosphere of a high humidity of 90% RH at 40.degree. C., the known metal halide GIC, considered as a stable compound in the atmosphere, was found to have a non-negligibly larger change of the resistance value with time. In the case of an electric conductor experimentally made from FeCl.sub.3 --GIC, the resistance value thereof increased by 30% when 100 hours passed.
Conventionally known metal halide GICs have inadequate stability in an atmosphere of high humidity as has been described above, which is a serious drawback for putting such GICs into practical use as conductive materials.